JPWO2013008493A1 - Reducing agent supply device and exhaust gas purification device for internal combustion engine - Google Patents

Abstract

Provided are a reducing agent supply device capable of reducing a state in which the pressure in the reducing agent supply passage greatly deviates from a target pressure, and an exhaust purification device provided with such a reducing agent supply device. A pump, a reducing agent injection valve, a reducing agent supply passage, a reducing agent return passage, and a pressure sensor are provided, and the liquid by the reducing agent injection valve is controlled so that the reducing agent pressure becomes a predetermined target pressure. In a reducing agent supply apparatus in which injection control of reducing agent is executed, a flow path throttle valve that is provided in a reducing agent return passage and whose opening degree is controlled by energization, and based on a difference between the reducing agent pressure and the target pressure Pump control means for feedback control of the output of the pump, and flow path throttle valve control means for controlling the opening of the flow path throttle valve in accordance with a change in the operation amount of the reducing agent injection valve.

Description

  The present invention relates to a reducing agent supply device for supplying a reducing agent to an exhaust passage of an internal combustion engine, and an exhaust gas purification device for an internal combustion engine provided with such a reducing agent supply device.

Conventionally, an exhaust passage of an internal combustion engine mounted on a vehicle or the like has been provided with an exhaust purification device for purifying nitrogen oxides (NO _x ) contained in the exhaust. One aspect of such an exhaust purification device, the NO _X purification catalyst which promotes the reduction reaction of NO _X, the reducing agent supply device for supplying a liquid reducing agent into the exhaust passage upstream of the NO _X purification catalyst And an exhaust emission control device.

  FIG. 13 is a view for explaining an example of the reducing agent supply device 220. The reducing agent supply device 220 includes a pump 223 that sucks up and pumps a liquid reducing agent such as unburned fuel or an aqueous ammonia solution stored in a tank 221 and a reducing agent that injects the pumped liquid reducing agent into an exhaust passage. An injection valve 225, a reducing agent supply passage 227 that guides the liquid reducing agent pumped by the pump 223 to the reducing agent injection valve 225, and a reducing agent return passage 229 connected between the reducing agent supply passage 227 and the tank 221. The pressure sensor 231 for detecting the reducing agent pressure Pu in the reducing agent supply passage 227 and the control device 240 for controlling the pump 223 and the reducing agent injection valve 225 are provided.

In the reducing agent supply device 220, NO _X amount and contained in the exhaust, such that the appropriate amount of the liquid reducing agent in consideration of reduction efficiency and the like of the NO _X is supplied to the just proportion exhaust passage In addition, it is necessary to execute injection control of the liquid reducing agent. Therefore, the liquid reducing agent is adjusted by adjusting the valve opening time of the reducing agent injection valve 225 while controlling the reducing agent pressure Pu supplied to the reducing agent injection valve 225 to be maintained at a predetermined target pressure Pu_tgt. The injection amount is controlled.

  Here, as control for maintaining the reducing agent pressure Pu at the target pressure Pu_tgt, the output of the pump 223 is feedback controlled based on the difference ΔPu between the reducing agent pressure Pu detected by the pressure sensor 231 and the target pressure Pu_tgt. There is a thing (refer patent document 1).

JP, 2011-117441, A (paragraph [0034])

  However, if it is attempted to maintain the reducing agent pressure Pu at the target pressure Pu_tgt only by feedback control of the output of the pump 223, when the injection amount of the liquid reducing agent greatly increases or decreases, the reducing agent pressure Pu becomes less than the target pressure Pu_tgt. There was a risk of disengagement. As a result, even when the reducing agent injection valve 225 is appropriately controlled in accordance with the target injection amount, the injection amount of the liquid reducing agent that is actually injected may deviate from the target injection amount. Furthermore, in the case where diagnostic control using the reducing agent pressure Pu or the like is executed, there is a risk that the diagnostic accuracy will be reduced.

  In view of such problems, the inventors of the present invention provide a flow restrictor in the middle of the reducing agent return passage, and respond to changes in the amount of operation of the reducing agent injection valve in conjunction with feedback control of the pump output. The present invention has been completed by finding that such a problem can be solved by controlling the opening of the flow path throttle valve. That is, an object of the present invention is to provide a reducing agent supply device capable of reducing a state in which the pressure in the reducing agent supply passage greatly deviates from a target pressure, and an exhaust purification device provided with such a reducing agent supply device. .

  According to the present invention, the pump that sucks up and pumps the liquid reducing agent in the tank, the reducing agent injection valve that injects the liquid reducing agent into the exhaust passage of the internal combustion engine, and the liquid reducing agent that is pumped by the pump. A reducing agent supply passage for guiding the reducing agent to the reducing agent injection valve, a reducing agent return passage connected between the reducing agent supply passage and the tank, and a reducing agent pressure in the reducing agent supply passage. A reductant return device in which the reductant supply device performs injection control of the liquid reductant by the reductant injection valve while controlling the reductant pressure to be a predetermined target pressure. A flow path throttle valve that is provided in the passage and whose opening is controlled by energization, and a pump control means that feedback-controls the output of the pump based on a difference between the reducing agent pressure and the target pressure; There is provided a reducing agent supply device comprising: a channel throttle valve control means for controlling an opening degree of the channel throttle valve in accordance with a change in an operation amount of the reducing agent injection valve. Can be solved.

  According to the reducing agent supply device of the present invention, the opening of the flow restrictor provided in the middle of the reducing agent return passage is changed to the change in the operation amount of the reducing agent injection valve together with the feedback control of the pump output. By adjusting accordingly, it is possible to solve the above-mentioned problems. That is, according to the reducing agent supply device of the present invention, the state in which the reducing agent pressure supplied to the reducing agent injection valve greatly deviates from the target pressure is reduced, and the liquid reducing agent is injected into the exhaust passage without excess or deficiency. It becomes like this. Further, when diagnostic control using the reducing agent pressure is executed, it is possible to prevent a decrease in diagnostic accuracy.

  Further, in the reducing agent supply apparatus according to the present invention, the flow path throttle valve control means always opens the flow path throttle valve at a predetermined basic opening, and the amount of operation of the reducing agent injection valve is large. It is preferable that the opening degree of the flow path throttle valve is temporarily reduced when increasing, and the opening degree of the flow path throttle valve is temporarily increased when the operation amount of the reducing agent injection valve is greatly reduced. .

  By controlling the flow restrictor in this way, the return flow rate flowing through the reducing agent return passage is changed according to the case where the injection amount of the liquid reducing agent is greatly increased or decreased, and the reducing agent pressure greatly deviates from the target pressure. Can be prevented.

  In the reducing agent supply apparatus according to the present invention, it is preferable that the flow path throttle valve control unit controls the flow path throttle valve at different times according to the amount of change in the operation amount of the reducing agent injection valve.

  By controlling the flow path throttle valve in this way, it becomes possible to use a flow path throttle valve having a relatively simple configuration, thereby improving the accuracy of pressure control and reducing the cost. it can.

  In the reducing agent supply apparatus according to the present invention, the flow path throttle valve control means controls the opening degree of the flow path throttle valve with a different operation amount corresponding to a change amount of the operation amount of the reducing agent injection valve. It is preferable.

  By controlling the flow restrictor in this way, the return flow rate is adjusted according to the increase rate or decrease rate of the injection amount of the liquid reducing agent, and the reducing agent pressure can be prevented from greatly deviating from the target pressure. .

  Further, in the reducing agent supply apparatus according to the present invention, when the reducing agent pressure exceeds an upper limit threshold or falls below a lower limit threshold when the opening of the flow path throttle valve is temporarily changed, It is preferable to include a correcting unit that corrects the time or the operation amount when changing the opening of the flow path throttle valve so that the reducing agent pressure falls within the upper limit threshold or the lower limit threshold.

  By controlling the flow restrictor in this way, the opening of the flow restrictor is changed according to the difference between the reducing agent pressure and the target pressure as a result of adjusting the opening of the flow restrictor. The time or the operation amount is corrected, and it is possible to prevent the reducing agent pressure from greatly deviating from the target pressure over a long period of time.

  Further, in the reducing agent supply device according to the present invention, the reducing agent supply device distributes the liquid reducing agent that is in a non-energized state during injection control of the liquid reducing agent to the reducing agent injection valve side. On the other hand, a flow path switching valve that causes the liquid reducing agent, which is energized at the end of the injection control of the liquid reducing agent, to flow to the tank side, and a flow path that performs current control to the flow path switching valve A switching valve control means, wherein the pump, the flow path throttle valve, and the flow path switching valve are configured as one unit, and the flow path switching valve control means and the flow path throttle valve control means are configured as a single unit. It is configured as a control device, and it is preferable that the flow path throttle valve and the flow path switching valve are controlled using a single harness.

  By configuring the reducing agent supply device in this manner, the reducing agent supply device according to the present invention can be configured without requiring an additional harness with respect to the conventional reducing agent supply device.

Another aspect of the present invention is an exhaust gas purification apparatus for an internal combustion engine comprising any one of the above-described reducing agent supply apparatuses and an NO _x purification catalyst for purifying nitrogen oxides in the exhaust gas.

  According to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, since the reducing agent supply device capable of reducing the state in which the reducing agent pressure supplied to the reducing agent injection valve greatly deviates from the target pressure, the liquid reducing agent is provided. Can be injected without excess and deficiency, and nitrogen oxides can be efficiently purified. In addition, according to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, since the reducing agent supply device as described above is provided, it is possible to accurately execute the diagnostic control using the reducing agent pressure. Can do.

It is a figure which shows the structure of the exhaust gas purification apparatus provided with the reducing agent supply apparatus concerning the 1st Embodiment of this invention. It is a block diagram which shows the structure of the electronic controller of the reducing agent supply apparatus concerning 1st Embodiment. It is a figure which shows the pressure change at the time of controlling a reducing agent pressure only by feedback control of an electromagnetic pump. It is a figure which shows the pressure change at the time of controlling a reducing agent pressure by controlling the opening degree of a flow-path throttle valve with feedback control of an electromagnetic pump. It is a figure which shows the pressure change at the time of controlling a reducing agent pressure by controlling the opening degree of a flow-path throttle valve with feedback control of an electromagnetic pump. It is a flowchart figure shown in order to demonstrate an example of the control method of the flow-path throttle valve in the reducing agent supply apparatus concerning 1st Embodiment. It is a flowchart figure shown in order to demonstrate an example in the case of restrict | squeezing the opening degree of the flow-path throttle valve in the reducing agent supply apparatus concerning 1st Embodiment. It is a flowchart figure shown in order to demonstrate an example in the case of enlarging the opening degree of the flow-path throttle valve in the reducing agent supply apparatus concerning 1st Embodiment. It is a block diagram which shows the structure of the electronic controller of the reducing agent supply apparatus concerning 2nd Embodiment. It is a flowchart figure shown in order to demonstrate an example in the case of restrict | squeezing the opening degree of the flow-path throttle valve in the reducing agent supply apparatus concerning 2nd Embodiment. It is a flowchart figure shown in order to demonstrate an example in the case of enlarging the opening degree of the flow-path throttle valve in the reducing agent supply apparatus concerning 2nd Embodiment. It is an electrical circuit diagram in the reducing agent supply apparatus concerning 3rd Embodiment. It is a figure which shows the structure of the exhaust gas purification apparatus provided with the conventional reducing agent supply apparatus.

DESCRIPTION OF EMBODIMENTS Embodiments relating to a reducing agent supply device and an exhaust gas purification device for an internal combustion engine according to the present invention will be specifically described below with reference to the drawings.
In addition, what is attached | subjected with the same code | symbol in each figure has shown the same component unless there is particular description, and description is abbreviate | omitted suitably.

[First Embodiment]
1. Overall Configuration of Exhaust Gas Purification Device FIG. 1 is a diagram for explaining the configuration of an exhaust gas purification device 10 including a reducing agent supply device 20 according to a first embodiment of the present invention.
In FIG. 1, an exhaust purification device 10 is a device for purifying NO _x in exhaust gas, and is provided in an exhaust passage 3 of an internal combustion engine such as a diesel engine (not shown). The exhaust purification device 10 includes a NO _X purification catalyst 13 interposed in the middle of the exhaust passage 3 and a reducing agent supply device for supplying a liquid reducing agent into the exhaust passage 3 upstream of the NO _X purification catalyst 13. 20.

The NO _x purification catalyst 13 is a catalyst having a function of promoting decomposition of NO _{x in} the exhaust. As the NO _x purification catalyst 13, a NO _x selective reduction catalyst, a NO _x storage catalyst, or the like is mainly used. The NO _x selective reduction catalyst is a catalyst that adsorbs the reducing agent and selectively reduces the flowing NO _x by the reducing agent. In the case of using the NO _x selective reduction catalyst, an aqueous urea solution or unburned fuel (HC) is used as the liquid reducing agent.

Further, NO _X storage catalyst, while the air-fuel ratio of the exhaust gas is occluded NO _X in the exhaust gas in the state of the fuel-lean, unburned fuel with the air-fuel ratio of the exhaust gas to release NO _X in the state of the fuel-rich (HC) Is a catalyst that reduces NO _x in the exhaust gas. In the case of using the NO _x storage catalyst, unburned fuel (HC) is used as the liquid reducing agent.

  The reducing agent supply device 20 includes a tank 21 in which the liquid reducing agent is accommodated, a pump unit 30 that sucks up and pumps the liquid reducing agent, and a reducing agent injection valve 25 that injects the pumped liquid reducing agent into the exhaust passage 3. And. The pump unit 30 includes an electromagnetic pump 23, a flow path switching valve 33, and a flow path throttle valve 35. The electronic control device 40 controls driving of the reducing agent injection valve 25, the electromagnetic pump 23, the flow path switching valve 33, and the flow path throttle valve 35.

  A first reducing agent supply passage 27 is provided between the tank 21 and the electromagnetic pump 23, and a second reducing agent supply passage 28 is provided between the electromagnetic pump 23 and the reducing agent injection valve 25. . In addition, a reducing agent return passage 29 whose other end is connected to the tank 21 is branched in the middle of the second reducing agent supply passage 28.

  The pressure sensor 31 is provided in the second reducing agent supply passage 28 in order to detect the pressure of the reducing agent supplied to the reducing agent injection valve 25. In the reducing agent supply apparatus 20 according to the present embodiment, the pressure sensor 31 is provided in the pump unit 30, but may be provided at any position in the second reducing agent supply passage 28.

  The flow path switching valve 33 flows in the forward direction in which the liquid reducing agent pumped by the electromagnetic pump 23 flows from the tank 21 side to the reducing agent injection valve 25 side, and from the reducing agent injection valve 25 side to the tank 21 side. It has a function of switching to the reverse direction. In the reducing agent supply apparatus 20 according to the present embodiment, the flow path switching valve 33 communicates the first reducing agent supply passage 27 to the inlet side of the electromagnetic pump 23 in a non-energized state, thereby providing a second reducing agent supply passage. 28 communicates with the outlet side of the electromagnetic pump 23, while the first reducing agent supply passage 27 communicates with the outlet side of the electromagnetic pump 23 in the energized state, and the second reducing agent supply passage 28 communicates with the inlet side of the electromagnetic pump 23. Communicate with.

  That is, in the operating state of the internal combustion engine, the electronic control unit 40 cuts off the energization to the flow path switching valve 33 so that the liquid reducing agent can be supplied to the reducing agent injection valve 25. On the other hand, when the internal combustion engine is stopped, the electronic control unit 40 energizes the flow path switching valve 33 so that the liquid reducing agent in the reducing agent supply device 20 can be collected in the tank 21.

  The configuration for recovering the liquid reducing agent when the internal combustion engine is stopped is not limited to the method of providing the flow path switching valve 33. For example, the liquid reducing agent can be collected by rotating the electromagnetic pump 23 in the reverse direction.

  The electromagnetic pump 23 pumps the liquid reducing agent at a predetermined output by energization control by the electronic control unit 40. During the injection control of the liquid reducing agent, the output of the electromagnetic pump 23 is feedback controlled so that the reducing agent pressure Pu detected by the pressure sensor 31 is maintained at a predetermined target pressure Pu_tgt set in advance. Specifically, the electronic control unit 40 is configured to generate an electromagnetic pump based on a difference ΔPu between the reducing agent pressure Pu detected by the pressure sensor 31 and a predetermined target pressure Pu_tgt set in advance during the injection control of the liquid reducing agent. 23 output is PID controlled. When recovering the liquid reducing agent, the electronic control unit 40 performs control so that the electromagnetic pump 23 is driven with a predetermined output.

  The reducing agent injection valve 25 is opened by energization control and injects the liquid reducing agent into the exhaust passage 3. In the reducing agent supply apparatus 20 according to the present embodiment, the electronic control unit 40 obtains the target injection amount Qdv_tgt based on a predetermined arithmetic expression and assumes that the reducing agent pressure Pu is the target pressure Pu_tgt. For each predetermined injection cycle, a drive duty ratio corresponding to the target injection amount Qdv_tgt is determined, and energization control of the reducing agent injection valve 25 is performed. In this case, the drive duty ratio corresponds to the operation amount of the reducing agent injection valve 25. The drive duty ratio of the reducing agent injection valve 25 means the ratio of the valve opening time during one injection cycle.

  The flow path throttle valve 35 is an electromagnetic flow path throttle valve capable of adjusting the opening degree of the valve by energization control. The electronic control unit 40 controls the opening degree of the flow path throttle valve 35 according to the change in the drive duty ratio of the reducing agent injection valve 25 during the liquid reducing agent injection control. Further, the electronic control unit 40 controls the flow path throttle valve 35 so as to have a predetermined opening degree at the time of controlling the injection of the liquid reducing agent.

  In the reducing agent supply apparatus 20 according to the present embodiment, the output of the electromagnetic pump 23 is controlled while circulating the liquid reducing agent through the reducing agent return passage 29, and the reducing agent pressure Pu is set to the target pressure Pu_tgt. It is meant to be maintained. That is, at the time of controlling the injection of the liquid reducing agent, the flow path throttle valve 35 is not completely closed and is always open.

  FIG. 2 shows the configuration of the electronic control unit 40 in functional blocks. The electronic control unit 40 is configured around a known microcomputer, and includes a flow path switching control means 41, a pump control means 43, a reducing agent injection valve control means 45, and a flow path throttle valve control means. 47. Specifically, each of these means is realized by executing a program by a microcomputer.

  Although not shown, the electronic control device 40 includes a storage unit including a storage element such as a RAM or a ROM. In the storage means, a control program and various calculation maps are stored in advance, and calculation results by the respective means are written.

  Among these, the flow path switching valve control means 41 cuts off the power supply to the flow path switching valve 33 until the ignition switch is turned off after the ignition switch of the internal combustion engine is turned on. Is turned off, the flow path switching valve 33 is energized for a predetermined period.

  The pump control means 43 reads the reducing agent pressure Pu detected by the pressure sensor 31 at every predetermined calculation cycle, obtains a difference ΔPu between the reducing agent pressure Pu and a preset target pressure Pu_tgt, and determines the electromagnetic pump 23. Output PID control is executed. In the present embodiment, the pump control means 43 controls the output of the electromagnetic pump 23 by calculating a drive duty representing the pump rotation speed as a target output by calculation.

Reducing agent injection valve control means 45, NO _X flow rate and obtained based on the operating state or the like of the NO _X concentration sensor or the internal combustion engine at every predetermined calculation cycle, the temperature of the NO _X purification catalyst 13, based on other information The target injection amount Qdv_tgt of the liquid reducing agent is obtained, and the drive duty ratio of the reducing agent injection valve 25 is controlled based on the target injection amount Qdv_tgt. The driving duty ratio obtained at this time is determined based on the target injection amount Qdv_tgt, assuming that the pressure of the liquid reducing agent supplied to the reducing agent injection valve 25 is the target pressure Pu_tgt.

  The flow path throttle valve control means 47 responds to the amount of change between the current drive duty ratio of the reducing agent injection valve 25 and the drive duty ratio of the reducing agent injection valve 25 in the previous calculation cycle. To control the opening degree. The calculation cycle before the predetermined number of times can be set to an optimal value according to the length of the calculation cycle, the required accuracy of pressure control, and the like. In the reducing agent supply apparatus 20 according to the present embodiment, the opening degree of the flow path throttle valve 35 can be switched in three stages. Specifically, the opening degree can be switched in three stages: a first opening degree Open State, a second opening degree (basic opening degree) Default State, and a third opening degree Close State. The degree is set such that the first opening degree Open State> second opening degree (basic opening degree) Default State> third opening degree Close State> 0.

  The flow restrictor control means 47 basically sets the opening of the flow restrictor 35 to the basic opening Default State, and when the drive duty ratio of the reducing agent injection valve 25 greatly increases, the opening is temporarily set. Therefore, the third opening degree Close State is switched to suppress the reduction of the reducing agent pressure Pu. On the other hand, when the drive duty ratio of the reducing agent injection valve 25 greatly decreases, the opening degree is temporarily switched to the first opening degree Open State so that the increase in the reducing agent pressure Pu is suppressed.

  Further, in the reducing agent supply apparatus 20 according to the present embodiment, the amount of increase in the drive duty ratio of the reducing agent injection valve 25 when the opening degree of the flow path throttle valve 35 is switched to the third opening degree Close State. And a first basic map M1 that preliminarily defines a relationship between the opening amount of the flow restrictor 35 and the time Tbf_close for maintaining the opening degree of the flow passage throttle valve 35 temporarily. Further, when the opening degree of the flow path throttle valve 35 is switched to the first opening degree Open State, the decrease amount of the drive duty ratio of the reducing agent injection valve 25 and the opening degree of the flow path throttle valve 35 are temporarily set. A second basic map M2 that preliminarily defines the relationship with the time Tbf_open that is kept large is stored in the storage means.

  These basic maps are obtained, for example, by experiments in advance for a time during which the reducing agent pressure Pu greatly deviates from the target pressure Pu_tgt when the drive duty ratio of the reducing agent injection valve 25 is changed while performing feedback control of the electromagnetic pump 23. And can be created based on this result. After obtaining the amount of change in the drive duty ratio of the reducing agent injection valve 25, the flow restrictor control means 47 further refers to the first basic map M1 or the second basic map M2 and sets the flow restrictor 35. A time for changing the opening is obtained, and the opening of the flow restrictor 35 is switched.

2. Next, in order to maintain the pressure supplied to the reducing agent injection valve 25 at the target pressure Pu_tgt in the reducing agent supply device 20 according to the present embodiment, the control performed by the electronic control device 40 is performed. The contents will be described in detail.

(1) Pressure Change FIG. 3 shows the pressure change when the reducing agent pressure Pu is controlled only by the feedback control of the electromagnetic pump 23 while the drive duty ratio of the reducing agent injection valve 25 changes. 4 and 5 show the pressure change when the reducing agent pressure Pu is controlled by controlling the opening degree of the flow path throttle valve 35 in conjunction with the feedback control of the electromagnetic pump 23. FIG. 3 corresponds to the period of the region A surrounded by the one-dot chain line in FIG. 3, and FIG. 5 corresponds to the period of the region B surrounded by the two-dot chain line in FIG.

  As shown in FIG. 3, when the reducing agent pressure Pu is controlled only by the feedback control of the electromagnetic pump 23, when the drive duty ratio of the reducing agent injection valve 25 suddenly increases from 0% to 50% (region A), In the case where the pressure suddenly decreases from 50% to 0% (region B), the immediately following reducing agent pressure Pu deviates significantly from the target pressure Pu_tgt. In the case where the drive duty ratio of the reducing agent injection valve 25 suddenly increases from 0% to 50% (region A), after the reducing agent pressure Pu greatly deviates from the target pressure Pu_tgt, the reducing agent pressure Pu becomes the target. The amplitude repeats around the pressure Pu_tgt and is not attenuated.

  On the other hand, as shown in FIG. 4, when the feedback control of the electromagnetic pump 23 and the opening degree control of the flow path throttle valve 35 are used in combination, the drive duty ratio of the reducing agent injection valve 25 is 0% to 50%. In the case of sudden increase, the opening of the flow path throttle valve 35 is switched to the third opening Close State during the period of time Tbfv_close. As a result, the pressure drop in the second reducing agent supply passage 28 is suppressed, and the reducing agent pressure Pu is not greatly deviated from the target pressure Pu_tgt. Further, after that, the reducing agent pressure Pu is quickly attenuated toward the target pressure Pu_tgt.

  Further, as shown in FIG. 5, when the feedback control of the electromagnetic pump 23 and the control of the opening degree of the flow path throttle valve 35 are used in combination, the drive duty ratio of the reducing agent injection valve 25 suddenly increases from 0% to 50%. In the case of the increase, the opening degree of the flow restrictor 35 is switched to the first opening degree Open State during the period of time Tbfv_open. As a result, the pressure increase in the second reducing agent supply passage 28 is suppressed, and the reducing agent pressure Pu is not greatly deviated from the target pressure Pu_tgt.

(2) Flowchart Hereinafter, an example of the control method of the flow path throttle valve 35 executed by the electronic control device 40 provided in the reducing agent supply device 20 according to the present embodiment is shown in the flow charts of FIGS. A specific explanation will be given. The routine described below is always executed during operation of the internal combustion engine.
Although not shown in the following flowchart, feedback control of the output of the electromagnetic pump 23 is executed in parallel with the control of the flow path throttle valve 35.

  First, in step S11 of FIG. 6, the electronic control unit 40 starts injection control of the liquid reducing agent, and then in step S12, the opening degree of the flow path throttle valve 35 is changed to a second opening degree (basic opening degree) Default. In step S13, control of the flow path throttle valve 35 is started.

  Next, in step S14, the electronic control unit 40 calculates a difference ΔDVduty between the current drive duty ratio of the reducing agent injection valve 25 and the drive duty ratio of a predetermined calculation cycle before a predetermined number of times, and then in step S15. Then, it is determined whether or not the drive duty ratio difference ΔDVduty is less than a preset upper threshold. The upper threshold is a threshold for determining a state in which the reducing agent pressure Pu is likely to drop significantly due to a sudden increase in the injection amount of the liquid reducing agent, and is an appropriate value in consideration of the required accuracy of pressure control and the like. Set to

  In step S15, when the difference ΔDVduty is equal to or greater than the upper limit threshold (No determination), the process proceeds to step S17, and the electronic control unit 40 opens the flow path throttle valve 35 in order to prevent the reducing agent pressure Pu from decreasing. Control for further narrowing the degree is executed, and the process returns to step S13.

  FIG. 7 is a flowchart specifically showing an example of control for reducing the opening of the flow path throttle valve 35 executed in step S17. In this example, first, in step S21, the electronic control unit 40 sets the opening degree of the flow path throttle valve 35 to the third opening degree Close State. Next, in step S22, the electronic control unit 40 maintains the opening at the third opening Close State from the first basic map M1 based on the difference ΔDVduty of the driving duty ratio of the reducing agent injection valve 25. The duration time Tbfv_close is determined and set.

  Next, in step S23, the electronic control unit 40 determines whether or not the elapsed time T from the start of the control for reducing the opening degree of the flow path throttle valve 35 has reached the duration Tbfv_close. This step S23 is repeated until the elapsed time T reaches the duration Tbfv_close. When the elapsed time T reaches the duration Tbfv_close, the process proceeds to step S24, and the electronic control unit 40 increases the opening of the flow path throttle valve 35. After returning to the second opening (basic opening) Default State, the control for reducing the opening of the flow path throttle valve 35 is terminated.

  Returning to FIG. 6, when the difference ΔDVduty is less than the upper limit threshold value (Yes determination) in step S15, the process proceeds to step S16, and the electronic control unit 40 determines whether or not the difference ΔDVduty exceeds the lower limit threshold value. Determine. The lower threshold is a threshold for determining a state where the injection amount of the liquid reducing agent is suddenly decreased and the reducing agent pressure Pu is likely to increase significantly, and is an appropriate value in consideration of the required accuracy of pressure control and the like. Set to

  In step S16, when the difference ΔDVduty is equal to or lower than the lower limit threshold (No determination), the process proceeds to step S18, and the electronic control unit 40 opens the flow path throttle valve 35 in order to prevent the reducing agent pressure Pu from increasing. Control for enlarging the degree is executed, and the process returns to step S13.

  FIG. 8 is a flowchart specifically illustrating an example of control for expanding the opening degree of the flow path throttle valve 35 executed in step S18. In this example, first, in Step S31, the electronic control unit 40 sets the opening degree of the flow path throttle valve 35 to the first opening degree Open State. Next, in step S32, the electronic control unit 40 maintains the opening at the first opening Open State from the above-described second basic map M2 based on the difference ΔDVduty of the driving duty ratio of the reducing agent injection valve 25. The duration time Tbfv_open to be obtained is set.

  Next, in step S33, the electronic control unit 40 determines whether or not the elapsed time T from the start of the control for expanding the opening of the flow path throttle valve 35 has reached the duration Tbfv_open. This step S33 is repeated until the elapsed time T reaches the duration Tbfv_open. When the elapsed time T reaches the duration Tbfv_open, the process proceeds to step S34, and the electronic control unit 40 increases the opening of the flow path throttle valve 35. After returning to the second opening (basic opening) Default State, the control to increase the opening of the flow path throttle valve 35 is terminated.

  Returning to FIG. 6, when the difference ΔDVduty exceeds the lower limit threshold in step S <b> 16, the difference ΔDVduty of the drive duty ratio of the reducing agent injection valve 25 is within a predetermined range (lower limit threshold <ΔDVduty <upper limit threshold), and reduction. Since there is no possibility that the agent pressure Pu greatly deviates from the target pressure Pu_tgt, the process directly returns to step S13. Thereafter, the same calculation process is repeated according to the procedure described so far.

3. Effect of First Embodiment The reducing agent supply device 20 according to the first embodiment of the present invention described above is provided in the middle of the reducing agent return passage 29 in conjunction with feedback control of the output of the electromagnetic pump 23. Since the opening degree of the flow path throttle valve 35 is adjusted according to the difference ΔDVduty of the drive duty ratio of the reducing agent injection valve 25, the state where the reducing agent pressure Pu greatly deviates from the target pressure Pu_tgt is reduced. Can be possible. As a result, by executing the control of the reducing agent injection valve 25 on the assumption that the reducing agent pressure Pu is the target pressure Pt_tgt, the liquid reducing agent is injected into the exhaust passage 3 without excess or deficiency. . Further, in the case where various diagnostic controls using the reducing agent pressure Pu, such as clogging diagnosis of the reducing agent injection valve 25, are performed, it is possible to prevent a decrease in diagnostic accuracy. Therefore, it is possible to provide the exhaust purification device 10 that can execute the exhaust purification control with high accuracy.

  Moreover, according to the reducing agent supply apparatus 20 according to the first embodiment, the flow path throttle valve control means 47 of the electronic control unit 40 has the second throttle opening (basic opening) Default State and the flow path throttle valve. 35 is always opened, and when the drive duty ratio of the reducing agent injection valve 25 increases rapidly, the opening of the flow path throttle valve 35 is set to the third opening Close State, and the opening is temporarily set. When the drive duty ratio of the reducing agent injection valve 25 is rapidly reduced, the opening degree of the flow path throttle valve 35 is set to the first opening degree Open State to temporarily increase the opening degree. Yes. Therefore, it is possible to prevent the reducing agent pressure Pu from greatly deviating from the target pressure Pu_tgt by changing the return flow rate flowing through the reducing agent return passage 29 according to the case where the injection amount of the liquid reducing agent greatly increases or decreases.

  Further, according to the reducing agent supply device 20 according to the first embodiment, the flow path throttle valve control means 47 of the electronic control device 40 is at different times according to changes in the drive duty ratio of the reducing agent injection valve 25. The opening degree of the flow path throttle valve 35 is controlled. Therefore, it becomes possible to employ the flow path throttle valve 35 having a relatively simple configuration, so that the accuracy of pressure control can be improved and the cost can be suppressed.

[Second Embodiment]
The reducing agent supply apparatus according to the second embodiment of the present invention has the same basic configuration as that of the reducing agent supply apparatus according to the first embodiment, while the contents of control by the electronic control unit are the same. This is different from the case of the reducing agent supply apparatus according to the first embodiment. Hereinafter, while referring to FIG. 1 for the basic configuration, the reductant supply device according to the present embodiment will be described using the components in FIG. 1 as they are for the components other than the electronic control unit.

1. Configuration of Electronic Control Device In the reducing agent supply device according to the present embodiment, the electronic control device maintains the optimal control of the reducing agent pressure Pu in consideration of deterioration with time, manufacturing tolerance of each component, and the like. As described above, the durations Tbfv_close and Tbfv_open for temporarily reducing or increasing the opening of the flow path throttle valve 35 can be corrected.

  FIG. 9 is a functional block diagram showing the configuration of the electronic control unit 50 provided in the reducing agent supply apparatus according to the present embodiment. The electronic control unit 50 is configured around a known microcomputer, and includes a flow path switching control means 41, a pump control means 43, a reducing agent injection valve control means 45, and a flow path throttle valve control means. 47 and correction means 51. Specifically, each of these means is realized by executing a program by a microcomputer.

  Although not shown, the electronic control unit 50 includes a storage unit including a storage element such as a RAM or a ROM. In the storage means, a control program and various calculation maps are stored in advance, and calculation results by the respective means are written.

  Among these, the flow path switching control means 41, the pump control means 43, the reducing agent injection valve control means 45, and the flow path throttle valve control means 47 are respectively the same as those of the reducing agent supply apparatus according to the first embodiment. Since it can be configured in the same manner as the case, detailed description is omitted.

  When the maximum value or the minimum value of the reducing agent pressure Pu when the opening degree of the flow path throttle valve 35 is further reduced or expanded is exceeded, the correction means 51 changes the opening degree thereafter. The durations Close State and Open State are corrected.

2. Flowchart FIG. 6 shows the basic routine of the control method of the flow path throttle valve executed in the reducing agent supply apparatus according to the present embodiment, as in the case of the reducing agent supply apparatus according to the first embodiment. It is executed along the flowchart shown in the figure. However, the contents of step S17 for performing control for further reducing the opening degree of the flow path throttle valve 35 and step S18 for performing control for expanding the opening degree of the flow path throttle valve 35 are the reducing agents according to the first embodiment. It is different from the case of the supply device.

  First, an example of control performed in the reducing agent supply device according to the present embodiment when the opening degree of the flow path throttle valve 35 is further reduced will be described in detail with reference to the flowchart shown in FIG.

  In this example, first, in step S41, the electronic control unit 50 sets the opening degree of the flow path throttle valve 35 to the third opening degree Close State. Next, in step S42, the electronic control unit 50 determines the opening degree based on the first basic map M1 described above and the correction amount at this time based on the difference ΔDVduty of the drive duty ratio of the reducing agent injection valve 25. The duration Tbfv_close to be maintained at the third opening Close State is obtained and set.

  Next, in step S43, the electronic control unit 50 determines whether or not the reducing agent pressure Pu detected by the pressure sensor 31 is lower than the minimum pressure value Pu_min. The minimum pressure value Pu_min is a value that is updated each time the reducing agent pressure Pu shows a minimum value after the control for reducing the opening degree of the flow path throttle valve 35 is started this time. In step S43, when the reducing agent pressure Pu is equal to or higher than the stored pressure minimum value Pu_min (No determination), the process proceeds to step S45, while the reducing agent pressure Pu is stored in the stored pressure minimum value Pu_min. When it is less than (Yes determination), the process proceeds to step S44, and the reducing agent pressure Pu at that time is updated as the minimum pressure value Pu_min, and then the process proceeds to step S45.

  Next, in step S45, the electronic control unit 50 determines whether or not the elapsed time T since the start of the control for reducing the opening degree of the flow path throttle valve 35 has reached the duration Tbfv_close. If the elapsed time T has not reached the duration Tbfv_close in step S45 (No determination), the process returns to step S43, and steps S43 to S45 are repeated until the elapsed time T reaches the duration Tbfv_close.

  On the other hand, when the elapsed time T has reached the continuation time Tbfv_close in step S45 (Yes determination), the process proceeds to step S46, and the electronic control unit 50 increases the opening of the flow path throttle valve 35 to the second opening. Return to degree (basic opening) Default State. Thereafter, in step S47 to step S48, the update of the minimum pressure value Pu_min is continued along the same procedure as in step S43 to step S44. The update of the minimum pressure value Pu_min is repeated until it is determined in step S49 that the reducing agent pressure Pu indicates a value equal to or higher than the target pressure Pu_tgt (Yes determination).

  When it is determined in step S49 that the reducing agent pressure Pu is equal to or higher than the target pressure Pu_tgt, the process proceeds to step S50, and the electronic control unit 50 sets the stored pressure minimum value Pu_min to the pressure lower limit threshold Pu_min_thre. Determine whether it is below. The pressure lower limit threshold Pu_min_thre defines an allowable range when the reducing agent pressure Pu is greatly deviated from the target pressure Pu_tgt, and is set to an optimal value in consideration of an allowable error in pressure control and the like.

  In step S50, when the stored pressure minimum value Pu_min is equal to or greater than the pressure lower limit threshold Pu_min_thr (No determination), it can be considered that the pressure control functions effectively in the current setting. Then, the control for reducing the opening of the flow path throttle valve 35 is finished. On the other hand, when the stored pressure minimum value Pi_min is lower than the pressure lower limit threshold Pu_min_thr (Yes determination) in step S50, the process proceeds to step S51, and control for reducing the opening of the flow path throttle valve 35 is executed. The correction amount of the duration time Tbfv_close is calculated.

  That is, even when the opening amount of the flow path throttle valve 35 is throttled by the duration time Tbfv_close determined by the current setting, since the reduction of the reducing agent pressure Pu cannot be suppressed, the duration time Tbfv_close is long. The duration Tbfv_close is corrected so as to be.

  The correction amount may be obtained in any form, but may be a coefficient (> 0) for multiplying the value of the duration Tbfv_close obtained from the first basic map M1, for example. It is also possible to use a value to be added to the value of the duration Tbfv_close obtained from the first basic map M1. Further, the correction amount can be obtained according to the difference ΔPu_min between the stored minimum pressure value Pu_min and the pressure lower limit threshold Pu_min_thre, or can be increased stepwise by a predetermined amount. You can also.

  After the correction amount is obtained in step S51, in step S52, the electronic control unit 50 performs the correction so that the correction amount is reflected in the calculation of the duration Tbfv_close. Thus, the control for reducing the opening degree of the flow path throttle valve 35 is completed.

  Next, an example of control executed when the reducing agent supply apparatus according to the present embodiment increases the opening of the flow path throttle valve 35 will be specifically described with reference to the flowchart shown in FIG. .

  In this example, first, in step S61, the electronic control unit 50 sets the opening degree of the flow path throttle valve 35 to the first opening degree Open State. Next, in step S62, the electronic control unit 50 determines the opening based on the second basic map M2 described above and the correction amount at this time based on the difference ΔDVduty of the drive duty ratio of the reducing agent injection valve 25. The duration Tbfv_Open maintained at the first opening degree Open State is obtained and set.

  Next, in step S63, the electronic control unit 50 determines whether or not the reducing agent pressure Pu detected by the pressure sensor 31 exceeds the maximum pressure value Pu_max. The maximum pressure value Pu_max is a value that is updated every time the reducing agent pressure Pu shows a maximum value after starting the control for expanding the opening degree of the flow path throttle valve 35 this time. In step S63, when the reducing agent pressure Pu is equal to or lower than the stored pressure maximum value Pu_max (No determination), the process proceeds to step S65, while the reducing agent pressure Pu is stored in the stored pressure maximum value Pu_max. Is exceeded (Yes determination), the process proceeds to step S64, and the reducing agent pressure Pu at that time is updated as the maximum pressure value Pu_max, and then the process proceeds to step S65.

  Next, in step S65, the electronic control unit 50 determines whether or not the elapsed time T from the start of the control for expanding the opening of the flow path throttle valve 35 has reached the duration Tbfv_open. In step S65, when the elapsed time T has not reached the duration Tbfv_open (No determination), the process returns to step S63, and steps S63 to S65 are repeated until the elapsed time T reaches the duration Tbfv_open.

  On the other hand, when the elapsed time T has reached the continuation time Tbfv_open (Yes determination) in step S65, the process proceeds to step S66, and the electronic control unit 50 opens the opening of the flow path throttle valve 35 to the second opening. Return to degree (basic opening) Default State. Thereafter, in steps S67 to S68, the update of the maximum pressure value Pu_max is continued along the same procedure as in steps S63 to S64. The update of the maximum pressure value Pu_max is repeated until it is determined in step S69 that the reducing agent pressure Pu indicates a value equal to or lower than the target pressure Pu_tgt (Yes determination).

  In step S69, when it is determined that the reducing agent pressure Pu is equal to or lower than the target pressure Pu_tgt, the process proceeds to step S70, and the electronic control unit 50 sets the stored pressure maximum value Pu_max to the pressure upper limit threshold Pu_max_thre. It is determined whether or not it exceeds. The pressure upper limit threshold Pu_max_thre defines an allowable range when the reducing agent pressure Pu rises far from the target pressure Pu_tgt, and is set to an optimal value in consideration of an allowable error in pressure control and the like.

  In step S70, when the stored pressure maximum value Pu_max is equal to or greater than the pressure lower limit threshold Pu_max_thr (No determination), it can be considered that the pressure control functions effectively in the current setting. Then, the control for expanding the opening degree of the flow path throttle valve 35 is finished as it is. On the other hand, when the stored pressure maximum value Pi_max exceeds the pressure upper limit threshold Pu_max_thr (Yes determination) in step S70, the process proceeds to step S71, and control for increasing the opening degree of the flow path throttle valve 35 is executed. The correction amount of the duration time Tbfv_open at the time is determined.

  That is, even when the opening amount of the flow path throttle valve 35 is throttled by the duration time Tbfv_open determined by the current setting, the increase in the reducing agent pressure Pu cannot be suppressed, so that the duration time Tbfv_open is long. The duration Tbfv_open is corrected so that

  The correction amount may be obtained in any form, but may be a coefficient (> 0) for multiplying the value of the duration Tbfv_open obtained from the second basic map M2, for example. It is also possible to use a value to be added to the value of the duration Tbfv_open obtained from the second basic map M2. Further, the correction amount can be obtained in accordance with the difference ΔPu_max between the stored pressure maximum value Pu_max and the pressure upper limit threshold Pu_max_thre, or can be increased stepwise by a predetermined amount. You can also.

  After the correction amount is obtained in step S71, in step S72, the electronic control unit 50 performs the correction so that the correction amount is reflected in the calculation of the duration time Tbfv_open. Thereby, the control for expanding the opening degree of the flow path throttle valve 35 is completed.

3. Effects of the Second Embodiment The reducing agent supply apparatus according to the second embodiment of the present invention described above can only obtain the same effects as the reducing agent supply apparatus 20 according to the first embodiment. In addition, the times Tbfv_close, Tbfv_open for changing the opening degree of the flow path throttle valve 35 according to the state of the difference between the reducing agent pressure Pu and the target pressure Pu_tgt as a result of changing the opening degree of the flow path throttle valve 35. And the reducing agent pressure Pu can be prevented from greatly deviating from the target pressure Pu_tgt over a long period of time. Therefore, it is possible to provide an exhaust emission control device capable of accurately executing exhaust gas purification control over a long period of time even when individual differences in the reducing agent supply device or deterioration with time occur.

[Third Embodiment]
The basic configuration of the reducing agent supply apparatus according to the third embodiment of the present invention is the same as that of the reducing agent supply apparatus according to the first embodiment or the second embodiment. In the reducing agent supply apparatus according to the embodiment, the control of the flow path throttle valve and the control of the flow path switching valve are performed using a single harness.

  12A and 12B schematically show an electric circuit that connects the electronic control devices 40 and 50, the flow path switching valve 33, and the flow path throttle valve 35 in the reducing agent supply apparatus according to the present embodiment. FIG. Among these, FIG. 12A shows a state during the liquid reductant injection control, and FIG. 12B shows a state during the liquid reductant recovery control.

  A signal line 37 and a ground line 38 are disposed between the electronic control units 40 and 50 and the pump unit 30. A switch driver 39 is provided in the middle of the signal line 37 so that the connection of the signal line 37 can be switched by the flow path switching valve 33 or the flow path throttle valve 35.

  As shown in FIG. 12A, during the injection control of the liquid reducing agent, the signal line 37 is connected to the flow path throttle valve 35, and the electronic control devices 40 and 50 control the flow path throttle valve 35. It is possible. In addition, as shown in FIG. 12B, during the liquid reductant recovery control, the signal line 37 is connected to the flow path switching valve 33 side, and the electronic control devices 40 and 50 control the flow path switching valve 33. Control is possible.

  In the reducing agent supply apparatus according to the present embodiment, the first reducing agent supply passage 27 is communicated with the inlet side of the electromagnetic pump 23 in the non-energized state, and the second reducing agent supply passage 28 is connected to the outlet of the electromagnetic pump 23. A flow path switching valve that communicates with the first reducing agent supply passage 27 to the outlet side of the electromagnetic pump 23 and communicates the second reducing agent supply passage 28 with the inlet side of the electromagnetic pump 23 in an energized state. 33 is used. That is, since it is sufficient to connect the signal line 37 to the flow path switching valve 33 only during the period during which the liquid reductant recovery control is performed when the internal combustion engine is stopped, the flow path restriction is controlled during the liquid reductant injection control. Control is not performed simultaneously with the valve 35.

  Therefore, when the flow restrictor 35 is provided in the middle of the reducing agent return passage 29, a signal can be transmitted to the flow restrictor 35 using a harness that transmits a signal to the flow switching valve 33. Harness is not required. The reducing agent supply apparatus according to the present embodiment can obtain the same effect as the reducing agent supply apparatus according to the first embodiment and the second embodiment, and can reduce the cost. Become.

[Other embodiments]
The reducing agent supply device and the exhaust purification device according to the first to third embodiments described above show one aspect of the present invention and do not limit the present invention. It is possible to change arbitrarily within the range. The reducing agent supply device and the exhaust purification device according to the first to third embodiments can be modified as follows, for example.

(1) The components constituting the reducing agent supply device 20 and the exhaust purification device 10 described in the first to third embodiments, the set values and setting conditions of the electronic control devices 40 and 50 are merely examples. It can be arbitrarily changed.

(2) The reducing agent supply device 20 and the exhaust purification device 10 according to the first to third embodiments drive the reducing agent injection valve 25 using the first basic map M1 and the second basic map M2. The opening degree of the flow path throttle valve 35 is changed with durations Tbfv_close and Tbfv_open corresponding to the difference ΔDVduty of the duty ratio. The drive duty ratio may be varied according to the difference ΔDVduty. Alternatively, both the duration time and the opening degree may be varied according to the difference ΔDVduty of the drive duty ratio of the reducing agent injection valve 25. Even in the case of such control, it is preferable that the subsequent duration or the opening degree is corrected based on the result of changing the opening degree of the flow path throttle valve 35.

(3) The reducing agent supply device and the exhaust emission control device according to the third embodiment use the first basic map M1 and the second basic map M2 as they are, and add a coefficient to be multiplied or added as a correction amount. Although the values are used to correct the durations Tbfv_close and Tbfv_open, the correction method can be appropriately adopted even if it is other than this method. For example, it is also possible to prepare a plurality of maps for further restricting the opening degree of the flow path throttle valve 35 and a plurality of maps for enlargement, and perform correction by switching the map to be used.

Claims (7)

A pump that sucks up and pumps the liquid reducing agent in the tank, a reducing agent injection valve that injects the liquid reducing agent into an exhaust passage of an internal combustion engine, and the liquid reducing agent that is pumped by the pump. A reducing agent supply passage leading to the reducing agent, a reducing agent return passage connected between the reducing agent supply passage and the tank, and a pressure sensor for detecting a reducing agent pressure in the reducing agent supply passage. In the reducing agent supply device in which injection control of the liquid reducing agent by the reducing agent injection valve is performed while controlling the reducing agent pressure to be a predetermined target pressure,
A flow path throttle valve that is provided in the reducing agent return passage and whose opening degree is controlled by energization;
Pump control means for feedback-controlling the output of the pump based on the difference between the reducing agent pressure and the target pressure;
Channel throttle valve control means for controlling the opening of the channel throttle valve in accordance with a change in the operation amount of the reducing agent injection valve;
A reducing agent supply device comprising:   The flow path throttle valve control means always opens the flow path throttle valve at a predetermined basic opening, and the opening degree of the flow path throttle valve when the operation amount of the reducing agent injection valve greatly increases. 2. The reducing agent supply device according to claim 1, wherein when the operating amount of the reducing agent injection valve is greatly reduced, the opening degree of the flow path throttle valve is temporarily increased. .   3. The reducing agent supply according to claim 1, wherein the channel throttle valve control unit controls the channel throttle valve at different times according to a change amount of an operation amount of the reducing agent injection valve. apparatus.   The said flow-path throttle valve control means controls the opening degree of the said flow-path throttle valve with the different operation amount according to the variation | change_quantity of the operation amount of the said reducing agent injection valve. Reducing agent supply device.   When the reducing agent pressure exceeds the upper threshold or falls below the lower threshold when the opening of the flow path throttle valve is temporarily changed, the reducing agent pressure is changed to the upper threshold or the lower threshold after the next time. 5. The reducing agent supply device according to claim 3, further comprising a correction unit that corrects the time or the operation amount when the opening degree of the flow path throttle valve is changed so as to fall within the range. The reducing agent supply device circulates the liquid reducing agent that is in a non-energized state during injection control of the liquid reducing agent to the reducing agent injection valve side, while at the end of the injection control of the liquid reducing agent. A flow path switching valve that causes the liquid reducing agent that is energized and pressure-fed to flow to the tank side, and a flow path switching valve control means that performs energization control to the flow path switching valve,
The pump, the flow path throttle valve, and the flow path switching valve are configured as one unit,
The flow path switching valve control means and the flow path throttle valve control means are configured as one control device,
The reducing agent supply apparatus according to any one of claims 1 to 5, wherein the control of the flow path throttle valve and the control of the flow path switching valve are performed using a single harness. Exhaust purification apparatus for an internal combustion engine having a reducing agent supply device disclosed, and a NO _X purification catalyst for purifying nitrogen oxides in the exhaust to any one of claims 1 to 6.

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